git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@13826 f3b2605a-c512-4ea7-a41b-209d697bcdaa

tools/moltemplate/examples/misc_examples/pyramids_vs_gravity/README.TXT

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+   Description:
+
+This is a simulation of pyramid-shaped objects resting on an immobile surface
+(resembling graphene).  Each pyramid is built from spherical particles stacked
+like cannon-balls, or stacked fruit.  Ordinarily, the stack does not move 
+because the particles at the ground layer are immobilized.  However, 
+given an initial (small) perturbation the pyramids collapse in an avalanche.
+
+(In this example, the perturbation is due to shock because we (intentionally)
+ did not minimize the system before starting the simulation.  This shock 
+ causes an avalanche to occur approximately 5000 timesteps later.)
+
+The particles roll down the pyramid and bounce off the "ground". The bouncing
+is due to a repulsive external force which is added artificially.
+(See the "run.in" file.)  The simulation looks weird without something 
+to bounce off of.  So I added a graphene surface at the bottom as scenery. 
+(It does not exert any force on the atoms.)
+
+(Random comment: This could be a fun example to illustrate the Boltzmann
+ distribution.  Because there is no damping, in a small region, I'm guessing 
+ the particle heights should eventually approach the Boltzmann distribution 
+ for some temperature consistent with the initial potential energy of the 
+ system.)